DLLME-spectrophotometric determination of glyphosate residue in legumes

•Glyphosate herbicide was determined using DLLME and spectrophotometry.•The basic extraction method was adopted to microvolume.•There is no significant interference in the analysis.•The method was successfully applied to the legumes samples.

A new separation and pre-concentration method for spectrophotometric determination of glyphosate herbicide was developed. Glyphosate was converted into dithiocarbamic acid with CS2, followed by copper in the presence of ammonia to promote complex formation. This complex was collected in a CH2Cl2 organic drop and absorbance measured at 435 nm. The analytical parameters, such as the amount of NH3, Cu(II) and CS2, type of extraction solutions, and the ratio of dispersive and organic liquids were optimized. The calibration curve was linear in the range 0.5-10 mg l−1. The limits of detection and quantification were calculated from 3 s to 10 s criterions as 0.21 mg l−1 and 0.70 mg l−1, respectively. The developed method was applied to legume samples with the satisfactory recovery values of 98 ± 4-102 ± 3%.